It is known in the state of the art that the freshness of fruits and vegetables and other perishable food and agricultural materials can be preserved by the use of an environment rich in carbon dioxide. U.S. Pat. No. 5,489,399, hereby incorporated herein by reference in its entirety, discloses various materials useful in carbon dioxide gas generating compositions. This disclosure teaches that the carbon dioxide gas generating composition is usually packed into a bag made of nonwoven fabric, woven fabric, film formed with fine pores not passing a liquid therethrough or composite sheet of such materials and then placed in a package with fruit or vegetables. The disclosure teaches that either the alkali carbonate or the acid of the composition must be of low solubility, since if both are highly soluble the composition itself became liquid.